| Background:Hepatitis B virus (HBV) infection is a major public health problemaffecting millions of people worldwide. Following acote HBV infection,5% to l0% of the adult patients will develop persistent infection that maylead to chronic hepatitis, cirrhosis, and hepatocellular carcinoma.Although HBV vaccine is widely used to prevent the new infectionoccurrence, there are millions of hepatitis B patients who needcuring .Alltiviral therapy of chronic HBV infection remains an importantclinica1 problem because of the lack of efficacy of the currently availabletreatmellts .The sustained response to interferon is observed in only 30 % to40% of the patients. Nowadays, gene theraPy, including nuclear acidvaccine, antisence oligoadenylate chimera et al, is hotly researched inlabofatory, and it may be used to treat the patiellts in near fube. Bat inclinical, oral aniviral drugs are the most importam way tO cure the chronichepatitis B .Nucleoside analogs rePresent a new class of potellt amiviralagents Which provide new hope in the theraPy of chronic HBV infection.The first nucleoside analog tested as an amiviral agellt for patients withchronic hepatitis B was adenine arabinoside (ARA). This drug wasabandoned, because of failure of theraPy to have a sustained effect on thenatural history of chronic hepatitis B and disabling neuropathic side effects.A orally administered nucleoside analogs, larnivudine, which can inhibitHBV reverse transcriptase activity and have been found to inhibit HBVreplication with negligible side effect. But mutations in the YMDDpolymerase motif of HBV DNA emerge in aPproximatCly a third of patientstreated with larnivudine for a year. These patients may be candidates forcombination therapy with altemative antiviral agellts .To find new ami-HBV agents is necessary and important. In the study, we investigated theanti- HBV effect of a novel nucleoside analog: 6 -L-2',3'-dideoxy-5-fluoro-cytidine,which was shorten named by FDN in this article.Objective:To study the antiviral activity against hepatitis B virus and itscytotoxicity of a novel nucleoside analog: FDN .The drug was offered byprofessor Yong-lian Zhu, Department of Pharmacology, School ofMedicine, Yale University.Materials and Methods:We used 2.2.15 cell line as a cel1 mode1 of HBV. It can synthesis andsecrete HBV and all HBV marks. We designed five different densities ofFDN: 0.0008 u M, 0.004 u M, 0.02 P M, 0.l ll M, 0.5 P M, added theminto cell culture system. And we used Lamivudine as a positive conirol.After 2.2.l5 cell continuously co-cultured for l44 hours (Renew thecu1ture system once in 72 hours ). HBV DNA was determined byquantificative PCR .We detected the extracellular (in culture supematant)and intracellular HBV DNA separately. HBsAg and HBeAg in culturesuPematani were detected by radioimmune assays too. A groWthinhibition of 2.2.15 cell conducted by FDN was evaluated by MTTreduction assay.Rcsult:The anii HBV effectinon in culture supematant was concentration-depend in 0.0008 u M-0. l ll M. The 50% inhibition concentration (IC5o)against extracellular HBV DNA of FDN was 0.02 ll M, which was alittle higher than that of Lamivudine (The IC5o of lamivudine was 0.2 llM ). The IC5o of intracellular HBV DNA inhibition (*IC5o) was 0.009 PM. The concentration of HBsAg and HBeAg were both decreased, butthe alteration was later than HBV DNA. It was suggested that thechanges of two antigens were caused by the decreased HBV quantity. 'Theconcentration of FDN required to inhibit 50% 2.2.l5 cell growth inculture was 30 ll M, which was l500 times higher than the IC5o'Conclusion:FDN was shOwn to have potent inhibiting effect on of HBV DNArePlication, Which was a little higher than tha of LaminVUine. The50% cytotoxicity concentration(TC5o) of FDN to 2.2.l5 cell is l500times higher than IC5o, which suggestCd that FDN was safe to living cellwhen it was used as an anivir...
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